A pH-responsive polycarbonate nanoplatform enables sequential drug release for enhanced apoptotic cascade synergy in...

Tumor heterogeneity poses formidable challenges to effective cancer therapy, necessitating the implementation of combination regimens to achieve enhanced antitumor efficacy. Optimizing drug administration sequences is pivotal to harnessing synergistic effects and achieving superadditive therapeutic outcomes (1 + 1 > 2). Erlotinib, an epidermal growth factor receptor (EGFR) inhibitor, dynamically reprograms apoptotic pathways, sensitizing tumor cells to subsequent DNA-damaging agents like doxorubicin within a defined temporal window, thereby augmenting chemotherapy efficacy. To advance this strategy toward clinical relevance, we developed a pH-responsive nanoplatform (PEDHNPs) for sequential control of drug delivery. This system integrates a dual acid-responsive polymeric architecture comprising a hydrazone-linked polycarbonate conjugated with doxorubicin as a prodrug and a ketal-based polycarbonate enabling temporal regulation of drug release. Erlotinib is encapsulated within the hydrophobic core during micelle self-assembly. In the acidic tumor microenvironment, PEDHNPs rapidly liberate erlotinib via ketal hydrolysis, followed by sustained doxorubicin release through hydrazone cleavage. This orchestrated delivery enhances EGFR inhibition and activates caspase-8-mediated apoptosis, potentiating doxorubicin's antitumor effect. In vitro experiments showed that at a doxorubicin concentration of 80 µg/mL, PEDHNPs achieved a proliferation inhibition rate of 71.54 ± 0.42 % in A549 cells, which was significantly higher than that of the monotherapy groups (Erlotinib: 31.48 ± 0.19 %; Doxorubicin: 63.18 ± 1.04 %) and the control group with amide bond conjugation (54.21 ± 1.13 %). In the NSCLC mouse model, treatment with PEDHNPs resulted in a 95.1 % reduction in tumor volume compared to the control PBS group. These offer a promising paradigm for achieving precise cancer therapy through sequential drug delivery. STATEMENT OF SIGNIFICANCE: Tumor heterogeneity compromises the efficacy of monotherapies, necessitating rationally designed combination regimens. Optimizing drug administration sequences is critical for harnessing synergistic interactions and achieving superadditive therapeutic outcomes (1 + 1 > 2). Here, a pH-responsive polycarbonate-based nanoparticle (PEDHNP) incorporating hydrazone and ketal linkages was designed for sequential co-delivery of erlotinib and doxorubicin. This sequence-controlled release strategy achieves early EGFR inhibition followed by activation of caspase-8-mediated apoptosis, thereby potentiating the antitumor activity of doxorubicin. In vitro, PEDHNPs exhibited superior antiproliferative and proapoptotic effects compared with monotherapies, single-drug nanoparticles, and amide-linked nanoparticle controls. In vivo, PEDHNPs achieved marked tumor growth suppression in a non-small cell lung cancer model, establishing a versatile platform for precision oncology via sequential drug delivery.